a) Field of the Invention
The present invention relates to a method of manufacturing a thin film transistor matrix, and more particularly to a thin film transistor matrix and its method of manufacture that enables repairing a disconnection or breaking of a metal bus line pattern.
b) Description of the Related Art
Liquid crystal panels of the thin film transistor (TFT) matrix type are being developed mainly for lap-top type personal computers and for wall hanging televisions. The TFT has two types of gates: a bottom gate type having a gate electrode disposed under an active semiconductor layer via a gate insulating film; and a top gate type having a gate electrode disposed over an active semiconductor layer via a gate insulating film.
A source electrode and a drain electrode are generally formed on the active semiconductor layer on both sides of a gate electrode, the source/drain electrode being a lamination of a metal layer and a contact semiconductor layer having a high impurity concentration. One of the source/drain electrodes is connected to a data bus line, and the other is connected to a pixel electrode.
In this specification, the source/drain connected to the data bus line is called a drain, and the source/drain connected to the pixel electrode is called a source. The data bus line is called a drain bus line.
A TFT matrix type liquid crystal display panel has a plurality of drain bus lines and data bus lines crossing each other and formed on a transparent insulating substrate. The drain bus line is connected to the drain of a TFT, and the gate bus line is connected to the gate thereof Generally, the drain bus line and the drain electrode are made of the same conductive layer. The gate bus line and the gate electrode are also made of the same conductive layer.
In this specification, when a single bus line constitutes a plurality of gate bus line portions and a plurality of gate electrode portions, the gate bus line portions are collectively called a single gate bus line.
A glass substrate used for a liquid crystal panel has a large area so that it is difficult to perfectly prevent foreign particles from dropping on the substrate during the manufacturing processes. If foreign particles exist on the glass substrate surface during the conductive layer formation, the conductive layer is not deposited directly on the glass substrate, but is instead deposited on the foreign particles. After the foreign particles are removed by cleaning or the like, pin holes are formed in the conductive layer.
If such pin holes completely or nearly break a gate bus line or drain bus line, the liquid crystal panel has a line defect. If pin holes exist in a source/drain electrode, a pixel electrode or a gate electrode branched from a gate bus line, there is a high possibility of pixel defects. Such defects, particularly line defects, are likely to become fatal defects in the liquid crystal display panel.
As described above, it is difficult to perfectly prevent a mixture of foreign particles during manufacture processes of a liquid crystal display panel. Line defects are likely to become fatal defects in the liquid crystal display panel. It has been desired therefore to provide the structure and manufacture method of a liquid crystal display panel capable of repairing a defective bus line even if foreign particles drop on the substrate during the manufacturing processes of the liquid crystal display panel.